Just a month before three people were killed and more than 260 others injured when a pair of bombs ripped through the crowd near the finish line at the Boston Marathon, bombing suspect Dzhokhar Tsarnaev bragged to his friends that he knew how to build explosives, criminal complaints against three new suspects revealed today.

Buried in the footnotes of court documents filed against three friends of Dzhokhar's is a reference to a chilling statement one of the friends, Azamat Tazhayakov, made to investigators in the days after the deadly attack.

"Tazhayakov also informed the FBI agents that while eating a meal with Dzhokhar and [friend Dias] Kadyrbayev approximately one month prior to the Marathon bombing, Dzhokhar had explained to Kadyrbayev and Tazhayakov that he knew how to make a bomb," the court documents say.

The statement was one of many new details to emerge today after authorities arrested 19-year-olds Kadyrbayev, Tazhayakov and another friend, Robel Phillipos, for their alleged actions in the days after the bombing. All three appeared in a Boston court this afternoon.

Tazhayakov and Kadyrbayev were charged with conspiracy to obstruct justice for purportedly trying to get rid of a laptop and backpack full of fireworks belonging to Dzhokhar after one of them realized Dzhokhar may be involved in the bombing. Phillipos was charged with making false statements to federal investigators.

Also revealed in the complaint was a text message conversation between one of the friends and Dzhokhar three days after the deadly attack. That day, April 18, Kadyrbayev texted Dzhokhar to tell him he resembled a man seen in images the FBI was circulating of possible suspects in the attack, the complaint says.

"LOL," replied Dzhokhar. Kadyrbayev took that and other texts like "you better not text me" to be jokes, documents say. Dzhokhar also told Kadyrbayev to take whatever he wanted from his dorm room.

It wasn't until the Kadyrbayev, Tazhayakov and Phillipos were hanging out together in Dzhokhar's dorm room alone that they spotted fireworks with missing powder. According to a criminal complaint, that was when Kadyrbayev "knew" his friend was involved in the attack.

Prosecutors say Kadyrbayev decided to take the backpack containing fireworks "to help his friend [Dzhokhar] avoid trouble" and took the laptop because he didn't want Dzhokhar's roommate to think he was behaving suspiciously. The documents assert that later Kadyrbayev and Tazhayakov decided together to throw the backpack and fireworks in the trash.

Robert Stahl, an attorney for Kadyrbayev, said today his client was not aware Dzhokhar was a suspect in the bombing when he took the backpack and laptop and did not know the items might have been involved in a bombing or were of evidentiary value. Harlan Protass, an attorney for Tazhayakov, said that his client has cooperated fully with authorities and "looks forward" to the truth coming out in his case.

Prosecutors said Phillipos initially told federal investigators he did not remember going to Dzhokhar's room and then said the three friends went there but did not go in. In his fourth interview with investigators, however, Phillipos "eventually confessed that he had lied to the agents," the court documents say.

Kadyrbayev and Tazhayakov face up to five years in prison and Phillipos faces a maximum sentence of up to eight years if convicted, the DOJ said.

Authorities and experts said both of the bombs that exploded April 15 were relatively unsophisticated devices, likely at least partially constructed based on instructions widely available on the internet. Dzhokhar is accused of executing the attack with his older brother, Tamerlan, who authorities say may have been in contact with Islamic militants during a 2012 trip to Russia.

Late Tuesday, the Tsarnaev family was deciding what to do with Tamerlan's body.

Bella Tsarnaev, one of the young man's sisters, told ABC News in her first public statement that she and her sister Ailina have planned a proper Muslim burial for Tamerlan. The brothers' uncle, Ruslan Tsarni, told The Associated Press Tuesday the family would take the body, "We will do it. A family is a family."

When the Massachusetts Medical Examiner's Office was ready to release her husband's body, Tamerlan's widow Katherine Russell declined to take it herself, according to her attorney.

"It is Katherine Russell's wish that his remains be released to the Tsarnaev family, and we will communicate her wishes to the proper authorities," attorney Amato DeLuca said Tuesday. DeLuca also said Russell has been meeting with law enforcement and is providing "as much assistance to the investigation as she can."

The statement came as investigators said they may have pinpointed a turning point in Tamerlan's growth into alleged radical: a 2012 trip to Russia in which he may have had contact with Russian Islamists.

American officials said they are investigating whether Tamerlan had been in contact over the internet with a man named William Plotnikov, a Russian-Canadian and a fellow boxer, who had converted to Islam and joined the militant insurgency in the North Caucasus. Plotnikov was killed by Russian authorities while Tamerlan was in Russia, and Tamerlan left the country just days later.